I don't really have any suggestions for where to go, unfortunately, but I have an anecdotal story: While I was in Omaha I was part of a group that met for "#coworkingWednesdays" at a coffee shop. The shop was kind of out-of-the-way and didn't get a lot of traffic. We got to the know the owner, who appreciated the business even though we didn't buy much. They didn't serve food there, but we would usually all head out together at lunch time to get food somewhere else, then come back. It was very informal, people wold come and go during the day, and usually the group was quite small. It was a blast.
I would be interested in a weekly coworking meetup in the downtown SLC or Sugarhouse area. My suggestion for a downtown location is Salt Lake Roasting company, since they have a lot of seating upstairs.
I will say some of the new co-working spaces in downtown SLC are quite reasonable - I think it's only $175/month for shared desk space at Church & State, and I currently have do 40 hours a month at the Impact Hub (I come in about once a week) for $80. They have free coffee.
But these don't do you much good if you live down in Draper or something, and only want to cowork 1 day a week!
One final note: I came across an interesting startup the other day:
http://sparechair.me. It looks like it's aiming to me an AirBnB but for office/coworking space. There's almost no one on the service, but I like the idea.
Cheers,
Evan